Window of Opportunity

There are mysteries in the neutrino mass spectrum which a complementary, direct measurement can help unravel.

Oscillation Exp. only sensitive to m2

disappearance => oscillation => mass2-flavor mixing is much easier to write down

Astrophysics/Cosmologyno sterile standard model interactions, stable

Supernovaeonly applies to Dirac neutrinosmodel-dependent at supernuclear densities

… … Physics ...Physics ...

… … Experiment … Experiment … G-2 storage ring: state-of-the-art spectrometer at bargain prices

Beamline can be parasitic with SEB, easily switched to RHIC, FEB

An order of magnitude improvement in a fundamental constant

A stricter limit is part of this decade’s focus on neutrino physics

PRESENT

Atmospheric: =>Xand m2 ~.0012 - .008 eV2 SuperK: => slightly favored)

Solar Neutrino: e =>X and m2 ~eV2 or is it 10-11 eV2 ? (SNO may help)

LSND => e and m2 ~ .03-1.0 eV2

FUTURE

MINOS - Beams early 2004 CERN - Beams early 2005

K2K - 220 evts by 2005 (if m2 large)

MiniBoone in 2003, Boone in ??

The next Supernova - Tools to interpret and limit

Neutrino decay

e e e via Lo (minimal LR symmetric model) consistent with

Mass Density of Universe Primordial nucleosynthesis Microwave Bkgd Diffuse -ray Bkgd SN1987a

as long as m() > 35 keV (from Z-width)

Supernovae

For mX)> 10 keV, t ~ day => pulse is below background if SNO sees no delayed pulse, then take your pick: No X produced? Oscillated to (sterile)? They decayed? is massive?

Check out all those 17 keV papers for more exotic loopholes

Closing LoopholesClosing Loopholes

GF mm2

GF

mm2

0.5 ppmMuLan

0.38 ppm 10 ppm

It is, after all, a Fundamental Constant !It is, after all, a Fundamental Constant !

Its uncertainty affects our knowledge of other fundamental constants

For example:

* Mass of the pion as measured by decay of stopped ’s

* Gfermi

theoretical precision negligible compared to experimental variablesother electroweak variables, such as MZ, continue to improve

Direct Measurements are …more direct!

Current Limits

m(e) 4.35 - 15 eV Tritium -decay endpoint 23 eV TOF spread from SN1987A 0.5 - 9 eV Double -decay for Majorana ’s

m(170 keV (stopping ’s)

m( 18.2 MeV Inv. Mass of hadrons (e+e- Colliders)

Pure 2-body decay No model-dependent nuclear/atomic environment

Pions live a reasonably long time

DIRECT MEASUREMENTS OF M(

Pion Decay at RestParent momentum is well-known

Limited by the uncertainty in the pion mass

Pion Decay in FlightNeed to measure

pp Momentum Resolution limited by mult.scattering in detectors

Pion Decay at Rest

Series of experiments at PSI

1979: Daum et al. (Phys Rev D20 p.2692) Solution A Solution B

1984: Abela et al (Phys Lett B146 p.431)Solution A Solution B

1996: Assamagan et al. (Phys Rev D53 p.6065)Solution A Solution B

m2( 0.163 + 0.080 MeV/c2)2

m()250 keV/c2

m2(+ 0.13 + 0.14MeV/c2)2

m()570 keV/c2

m2(0.143 +0.024 0.016 + 0.023MeV/c2)2

m()170 keV/c2

1982: Anderhub et al. Phys Lett B114 p.76

Pion Decay in Flight

m2( 0.14 + 0.20MeV/c2)2

m(500 keV/c2

2002: BNL g-2 Neutrino Mass Experiment?

m(8 keV/c2

If SuperK definitively proves =>m2~.007) Then this experiment reduces the neutrino mass limit

by 3 orders of magnitude!

Highlights of the Experimental Technique

• Translate p to r in 0.1 ppm uniform B-Fieldno multiple scatteringno need to measure decay angle or location

• Reference each to parent slow extraction

• In situ alignmentprotons (7 ns/turn late) prescaled undecayed pionsremote positioning of active vetoesremote angular adjustment of detector

• Position resolution from silicon1.4 m SSD

• Time resolution from scintillators and PMT’stight triple coincidence triggerTDC’s on all vetoes and embedded

hodoscope

In a perfectly uniform B-fieldAny charged particle returns to origin independent of B, p,

* Origin can produce a range of angles and momenta * Uniformity is more important than value of B* 1st harmonic (and other nonuniformities) are always monitored using residuals of prescaled pions and undecayed protons

“origin”

G-2 Storage Ring

G-2 Experiment Weak-focussing Storage Ring: Muons stored for 800 s

Quadrupoles Muon Kicker

NuMass Experiment Spectrometer: observed evt-by-evt

No Quads Pion kicker

Same Momentum - 3 GeVretain excellent shimming and B-field uniformity0.1 ppm over 4.5 cmTrolley runs in vacuum to map fieldFixed probes to track changes

Active shimming and thermal insulation to minimize change

“Pion Kicker”

p = -16.2 MeV/c X/Xo = 14.7 % (rms) = 1.56 mr

Put pions on orbit using dE/dx Injection

5.2 cm Beryllium

orbit with degrader

orbit withoutdegrader

D

D

D depends on m()

undecayed

pions

decay ’s

Forward-going decay muons orbit a larger diameter byD

CM

q = 29.7 MeV/c

D p - p0.7 MeV/c 3.26 mm D p3 GeV/c 14 m

D -m2

D 2 q m

non-zero mshrinks D

0.04 mm for current limit

Conceptual Design

D undecayed

pions

decay ’s

Forward-going decay muons orbit a larger diameter byD

CM

q = 29.7 MeV/c

D p - p0.7 MeV/c 3.26 mm D p3 GeV/c 14 m

Conceptual Design

D

D -m2

D 2 q m

non-zero mshrinks D

0.04 mm for current limit

D depends on m()

Non-forward going muons are lower momentum

They move to the inside of S2

Also vetoed offline by the g-2 calorimeters and J veto

J-Veto

S1 S2

g-2 Cal’s

Injection

decay orbit

24 g-2 calorimetersrestrict late decays

identify electron bkginitial beam tuning C-veto: restrict

incoming ’s

J-veto: restrict early ‘s at large angles

J-cal: 2nd turn electron id

Beam counter

Experimental MethodExperimental Method

S1 S2

Trigger Hodoscope

2.56 cm

6.4 cm

Embedded Scintillator:2 mm Prescale Strips

Trigger pads

BerylliumDegrader

S2

S1

Silicon strip Detectors (S1, S2)(1.28 cm long vertical strips at 50 m pitch)

32 strips per Viking chipserial readout into 1 ADC

@40MHz = 0.8 s

Sample & Hold Readout System

Simple Standard Cheap

Beam Counter

S1 (ch 6)

S2 (ch 6)

S1 (ch 71)

S2 (ch 71)

Hodoscope

Trigger:latch data

O

O

O

O

150 ns

225 ns

1st turn:

1st turn:

2nd turn:

2nd turn:

Parasitic RunningParasitic Running

E949 Running Conditions25 Gev protons70 TP in a 4.1 s spill / 6.4 s cycle

E952 Parameters2.8 x 106 into g-2 ring/TP5.4 x 1012 for an 8 keV result

Triggers Offline

Entering Ring Detector +vetoes

8 x 106 part/s 1 x 106 part/s 1.8 x 105 s-1 910 s-1 42 s-1

400 Hz/strip 55 s/SSD 11 ms/SSD

100 MB/s 0.5 MB/s

Prescale in trigger

Instantaneous rates (100% extr. eff.)

Running Time

5% of SEB beam => 492 hrs (crystal extr. eff.)

Scintillator Hodoscope

Radial segmentation = 2 mm Vertical segmentation = 12.8 mm

• 4 ns gate for 3-fold coincidence triggerAccidentals at 0.004, flagged by beam counter

• Veto events r < 2mm to enrich eventsx 50 prescale => 0.5 MB/s or 37 DLT tapes

• Select readout SSD0.7% dead time1/10 data volume

• 1 ns timing resolution (TDC) + 2mm segmentationreject accidentals offline (another factor of .002)

Sources of Background

• Beam-gas scattersvacuum is 10-6 torr

• Injected p (27%)7 ns/turn slower

• Injected e (12%)lose 1 MeV/turn from SR (4.7 mm inward)identify in J-Veto calorimeter (or position)

• => e (= 64 s)injected (1%) and =>< 10 -4 of good events rejected by g-2 calorimeters

• => e(BR=1.2 x 10-4)low tail out to ~ 5 mm calorimeter at inner J-Veto

5 mm endpt (q=70 MeV/c)

SR shrinks it 2 mm

e

e

g-2 Calorimeters

Some Background Configurations

J-Calorimeter

ScheduleSchedule

Summer 2000 Test individual SSD’s at CERN

Spring 2001 Do tests at end of g-2 run (fast extraction)

Insert 2 SSD’s in rigid frame with removable “degrader” -inj, low intensity, no quads, no kickerNo degrader:J-veto Degrader: J-veto

Summer 2001 Test of crystal extraction for Slow Beam

2001 Build mosaic of SSDCustomize VA readout (chip run)Tests of detector at CERN test beam

2002 Engineering run - parasitic with E949 Crystal extraction: slow beam down V-lineFinal 5x5 SSD configuration with degrader in ring

2002 Physics run - parasitic or dedicated

Responsibilities

Beamline and Ring BNL

SSD and readout electronics CERN, Minnesota

Active Vetoes and Scint Trigger BU, Illinois, Tokyo IT ??

Feedthrus and positioners Tokyo IT, Heidelberg ??, BNL

DAQ and g-2 electronics Existing (Minnesota, BU)

Field Measurements Yale, Heidelberg, BNL

Orbital dynamics, Monte Carlo Cornell, BNL, Yale, NYU, Minn, BU

Analysis The team!

Goals of the 2001 Test Run

• Check out trigger and DAQ modifications

• Read out silicon microstrip prototype detector in g-2 conditions

• Beamline settings for pion injection link to position of pion and muon at detector and J-vetomost efficient angle thru inflector

• Map scattering background in g-2 Cal, FSD, J-Veto

• Practice tightening profile using beamline

• Practice tightening profile using current shims

• Inject positive pions at 0.5% above magic momentum

• Observe trigger hodoscope (TDC and ADC gives 2 rough profiles 150 ns apart)

• No degrader Find 1st pass pion distribution and 2nd pass muon distribution Some storage: tune on fast rotation in detectors Check lifetimes of lost muons vs positrons in FSD’s See pions at Flash Counter on 1st turn

• Degrader Find 1st pass pion and 2nd pass pion distribution No storage: Check lifetime of lost muon distribution No pions on Flash Counter Muons scraped off inner J-Veto after 1st pass and pions after 2nd

• Read out microstrip detector as well, but unable to do residuals..yet

• Gradually reduce emittance and then reduce intensity How low a rate can we get? Can we find the on-orbit protons 7 ns later?

• Watch FSD, PSD and CAL detectors, collect information on the scattered background - electrons? muons?

• Delay S2 microstrip trigger to remove 1st pass in S2

Problems: Fast extraction, high intensity, sec shaping timeConditions: No vacuum, no kicker, no quads, reverse B-field

PSD tiles

Removable Copper sheets

S2 Prototype SSD’s from CERN

g-2 Test setup

S1

12.8 mm

12.8 mm

Trigger tiles

Using VA-2 chip: 800 ns shaping time

Beam Counter

S1 (ch 6)

S2 (ch 6)

S1 (ch 71)

S2 (ch 71)

Hodoscope

Trigger S1

O

O

O

O

150 ns

225 ns

1st turn:

1st turn:

2nd turn:

2nd turn:

Trigger S2

More Accidentals and More Deadtime

Inflector

No Degrader

T0 J-Veto

collimator

Pion hits inflector

pion => muon residual profile

Muon on orbit

Flash Counter

Inflector

Degrader

T0 J-Veto

collimator

Pion on orbit

pion => pion residual profile

Muon hits J-Vetoon 1st turn

Flash Counter

pion 2nd time around